In conventional multi-car elevators, a speed of a first car, a distance from the first car to a second car, and a danger distance and a minimum distance that depend on the speed of the first car are calculated. Then, if the distance to the second car is less than or equal to the danger distance, the first car is made to perform an emergency stop using a safety device. If the distance to the second car is less than or equal to the minimum distance, an emergency safety device of the first car is activated. In addition, the danger distance is set based on an emergency stop operating curve, and the minimum distance is set based on an operating curve of the emergency safety device (see Patent Literature 1, for example).
In other conventional multi-car elevators, first and second overspeed references relating to a first car are decided based on a relative position of a second car relative to the first car. A relative speed of the first car relative to the second car is detected, and the relative speed and the first and second overspeed references are compared. A hoisting machine brake is activated if the relative speed exceeds the first overspeed reference, and an emergency safety device is activated if the relative speed exceeds the second overspeed reference (see Patent Literature 2, for example).